N-Confused Phlorin-Prodigiosin Chimera: meso-Aryl Oxidation and π-Extension Triggered by Peripheral Coordination

An N-confused phlorin isomer bearing a dipyrrin moiety at the α-position of the confused pyrrole ring ( 1 ) was synthesized. Pd^II and B^III coordination at the peripheral prodigiosin-like moiety of 1 afforded the corresponding complexes 2 and 3 . Reflux of 2 in triethylamine (TEA) converted the meso-phenyl into the Pd^II-coordinating phenoxy group to afford 4 . Under the same reaction conditions, TEA was linked to the α-position of the dipyrrin unit in 3 as an N,N-diethylaminovinyl group to afford 5 . Furthermore, peripheral coordination of B^III in 3 and 5 improved the planarity of the phlorin macrocycle and thus facilitated the coordination of Ag^III at the inner cavity to afford 3-Ag and 5-Ag , respectively. These results provide an effective approach for developing unique porphyrinoids through peripheral coordination.     

Chlorophyll‐Derived Yellow Phyllobilins of Higher Plants as Medium‐Responsive Chiral Photoswitches

The fall colors are signs of chlorophyll breakdown, the biological process in plants that generates phyllobilins. Most of the abundant natural phyllobilins are colorless, but yellow phyllobilins (phylloxanthobilins) also occur in fall leaves. As shown here, phylloxanthobilins are unique four‐stage photoswitches. Which switching mode is turned on is controlled by the molecular environment. In polar media, phylloxanthobilins are monomeric and undergo photoreversible Z/E isomerization, similar to that observed for bilirubin. Unlike bilirubin, however, the phylloxanthobilin Z isomers photodimerize in apolar solvents by regio‐ and stereospecific thermoreversible [2+2] cycloadditions from self‐assembled hydrogen‐bonded dimers. X‐ray analysis revealed the first stereostructure of a phylloxanthobilin and its hydrogen‐bonded self‐templating architecture, helping to rationalize its exceptional photoswitch features. The chemical behavior of phylloxanthobilins will play a seminal role in identifying biological roles of phyllobilins.     

以问题为载体,培养学生的科学探究能力——"伏安法测电阻"探究教学设计

1 设计思想 “探究学习方式特别强调问题在学习活动中的重要性．一方面强调通过问题来进行学习，把问题看作是学习的动力、起点和贯穿于学习过程的主线；另一方面通过学习来生成问题，把学习过程看成是发现问题、提出问题、分析问题和解决问题的过程．”物理教师应该是科学问题的开发者．有必要对一些探究的物理问题创设一些情境，让学生在观察和体验中有所发现，有所联想，萌发出科学问题；或者创设一些任务，让学生在完成任务中运用科学思维，自己提炼出应探究的科学问题．启发学生提出科学问题是非常重要的，这正如爱因斯坦所说的：“提出一个问题往往比解决一个问题更重要．因为解决问题也许是一个数学上或实验上的技能而已，而提出新问题，新的可能性，从新的角度去看待旧的问题，却需要有创造性的想象力，而且标志着科学的真正进步．”在“伏安法测电阻”的教学活动中，笔者以问题为载体，激活学生思维，培养学生的科学探究能力，取得了良好的教学效果．     

环烷酸对油水界面膜流变性质的影响研究

研究了环烷酸对油水界面膜界面张力、弹性模量、损耗模量以及界面膜破裂速率常数的影响,同时对环烷酸与沥青质之间的相互作用进行了测定。结果表明,环烷酸使得原油油水界面张力下降;弹性模量随着环烷酸加量以及振荡频率的增加都分别逐渐增大,并且最终都趋于平衡;在任何振荡频率值时,损耗模量都随着环烷酸加量先增大后减小;当环烷酸加量增加时,界面膜破裂速率常数降低。环烷酸与沥青质之间存在相互作用,随着环烷酸加量的增加,其对沥青质界面膜弹性模量的影响与对原油界面膜弹性模量的影响相似,表明环烷酸主要是通过与沥青质相互作用而促进乳状液稳定性的。     

用光谱学方法研究不同放电等离子体粒子约束

本文用光谱学方法研究在ＨＬ－１装置上ＬＨＣＤ及ＥＣＲＨ等离子体，弹丸注入等离子体，偏压电极与偏压孔栏等离子体粒子约束特性。结果表明：在弹丸注入使用正向偏压电极与偏压孔栏期间，等离子体粒子约束行到改善，较低密度下（＾ｎｅ＜２．０×１０＾１＾３ｃｍ＾－＾３），ＬＨＣＤ脉冲期间粒子约束得到改善；而当密度＾－ｎｅ大于２．０×１０＾１＾３ｃｍ＾－＾３时，等离子体约束变坏。ＥＣＲＨ脉冲期间粒子约束得不到改善。     

Electrodeposition of CuInSe2 films by an alternating double-potentiostatic method using nearly neutral electrolytes

One step electrodeposition with an alternating double-potentiostatic(DPSED) program was used to prepare CuInSe₂ thin films in nearly neutral aqueous electrolytes with sodium citrate complex. Linear sweep voltammetry(LSV) was measured to probe voltammetric properties of electrolytes with respect to Cu, In and Se individual precursor and their mixed solutions. Compositional and structural characteristics of the as-deposited and annealed films at 400 °C in Ar atmosphere for 0.5 h were analyzed by XRD and XPS. The results showed that reduction of Cu²⁺ to Cu⁺ at one potential point of ?800 mV and subsequently formation of CuIn alloy as well as metal In and amorphous Se at the other potential point of ?1400 mV were responsible for synthesis of CISe chalcopyrite. Composition self-regulation made DPSED films have three elements co-deposition and more uniform element distribution, which promoted chalcopyrite CISe formation.     

Some comparison theorems for K?hler manifolds

In this work, we will verify some comparison results on K?hler manifolds. They are: complex Hessian comparison for the distance function from a closed complex submanifold of a K?hler manifold with holomorphic bisectional curvature bounded below by a constant, eigenvalue comparison and volume comparison in terms of scalar curvature. This work is motivated by comparison results of Li and Wang (J Differ Geom 69(1):43–47, 2005).     

On-line Time Differential Perturbed Angular Correlation with Light Probe Nucleus 19F

An on-line time differential perturbed angular correlation technique has been developed with the light probe nucleus ¹⁹F. The first on-line TDPAC measurement was carried out to determine the field gradient in Cd and quadrupole moment of ¹⁹F (0.197 MeV: I ^π = 5/2⁺, T_1/2 = 89 ns). This revised version was published online in September 2006 with corrections to the Cover Date.     

2′-O-Methyl modified guide RNA promotes the single nucleotide polymorphism (SNP) discrimination ability of CRISPR–Cas12a systems

The CRISPR–Cas12a system has been widely applied to genome editing and molecular diagnostics. However, off-target cleavages and false-positive results remain as major concerns in Cas12a practical applications. Herein, we propose a strategy by utilizing the 2′-O-methyl (2′-OMe) modified guide RNA (gRNA) to promote the Cas12a''s specificity. Gibbs free energy analysis demonstrates that the 2′-OMe modifications at the 3′-end of gRNA effectively suppress the Cas12a''s overall non-specific affinity while maintaining high on-target affinity. For general application illustrations, HBV genotyping and SARS-CoV-2 D614G mutant biosensing platforms are developed to validate the enhanced Cas12a''s specificity. Our results indicate that the 2′-OMe modified gRNAs could discriminate single-base mutations with at least two-fold enhanced specificity compared to unmodified gRNAs. Furthermore, we investigate the enhancing mechanisms of the 2′-OMe modified Cas12a systems by molecular docking simulations and the results suggest that the 2′-OMe modifications at the 3′-end of gRNA reduce the Cas12a''s binding activity to off-target DNA. This work offers a versatile and universal gRNA design strategy for highly specific Cas12a system development.

This study illustrates that 2′-O-methyl modified gRNAs improve the specificity of the CRISPR–Cas12a system (mg-CRISPR) via suppressing the Cas12a''s affinity to off-target DNA and provides an efficient strategy for high-specificity gRNA design.